Lift truck load lifting mechanism

ABSTRACT

Mechanism for tilting a cantilever type load lifting carriage on the extensible mast of a lift truck comprises a pair of tie bars mounted for vertical movement on the mast, a pair of links pivoted onto each tie bar, the links of each bar converging vertically and being pivoted onto an apron on the carriage. A pivotally mounted hydraulic ram is nested between each tie bar and an adjacent mast member, the rams being operable to cause vertical movement and consequently tilting of the apron and carriage.

United States Patent 11 1 Ramsey 1 1 Oct.2l, 1975 1 1 LIFT TRUCK LOAD LIFTING MECHANISM [75] Inventor: Keith E. Ramsey, Jackson, Mich.

[73] Assignee: The Knickerbocker Company,

Jackson, Mich.

[22] Filed: Sept. 28, 1972 [21] Appl. No.: 292,944

Related U.S. Application Data [60] Division of Ser. No. 104,118, Jan. 5, 1971, Pat. No. 3,727,781, which is a continuation of Ser. No. 660,630, Aug. 15, 1967, abandoned.

[52] U.S. Cl. 214/701 P; 74/519 [51] Int. Cl 86619/16 [58] Field of Search 214/660, 670, 671, 672,

[56] References Cited UNITED STATES PATENTS 1,875,103 8/1932 Mosel 214/701 P 2,001,803 5/1935 Stephens...... 214/D1G. 10 2,752,058 6/1956 Gibson 214/730 2,788,909 4/1957 Kughler 214/731 3,225,949 12/1965 Erickson et a1... 214/660 3,250,409 5/1966 Beard et al i 74/99 R 3,366,260 1/1968 Salna et a1. 214/671 3,759,110 9/1973 Davis 74/99 R Primary Examiner-Robert J. Spar Assistant Examiner-Lawrence J. Oresky Attorney, Agent, or Firm-Barnes, Kisselle, Raisch & Choate [5 7] ABSTRACT Mechanism for tilting a cantilever type load lifting carriage on the extensible mast of a lift truck comprises a pair of tie bars mounted for vertical movement on the mast, a pair of links pivoted onto each tie bar, the links of each bar converging vertically and being pivoted onto an apron on the carriage. A pivotally mounted hydraulic ram is nested between each tie bar and an adjacent mast member, the rams being operable to cause vertical movement and consequently tilt ing of the apron and carriage.

5 Claims, 7 Drawing Figures Patent all" F mm- Sheet 1 of 6 HGI nwillliiilij j m"- E? n E: \Q

US Patent Oct. 21, 1975 Sheet 4 of6 U.S. Patent 0m. 21, 1975 Sheet 6 of6 3,913,765

.HQHBHQW LIFT TRUCK LOAD LIFTING MECHANISM This application is a division of application Ser. No. 104,118 filed Jan. 5, l97l and entitled Lift Truck Load Lifting Mechanism", now U.S. Pat. No. 3,727,781, which issued Apr. 17, 1973, the said application Ser. No. 104,] 18 in turn being a continuation of application Ser. No. 660,630 filed Aug. 15, 1967 of the same title, now abandoned.

An object of the present invention is to provide an improved load lifting mechanism for industrial and/or off-the-road lift trucks of the type having an extensible load lifting mast and associated load lifting chains actuated by a hydraulic ram to lift a load supported in cantilever fashion on a carriage of the mast wherein loadinduced bending stresses are counterbalanced by forces transmitted in tension through the load lifting chains to thereby provide, in conjunction with other features of the invention, a load lifting mechanism which results in: (I) an economical and lightweight construction which is efficient and reliable in operation, (2) less strain on the mast parts and truck frame and axle, (3) an increased load lifting capacity, (4) greater stability, (5) lower center of gravity, (6) less power to raise the load, (7) faster lift speed, (8) a smaller oil reservoir in the hydraulic supply system, (9) adaptability to a variety of existing truck designs, (10) a greater range of load lifting capacities for a given design of truck and mast, (l l greater off-center load ratings both fore and aft and side to side, (12) a greater margin of safety to the operator as well as the equipment and l3) improved visibility.

Another object is to provide an improved tilting carriage mechanism for lift truck masts which pivots the load carrier on the carriage substantially about the center of gravity of the load, thereby reducing the power required to actuate the tilting carriage, and which minimizes the space and structural requirements of the carriage.

A further object is to provide an improved lift truck equipped with a counterbalanced load lifting mechanism of the aforementioned character which cooperates with an overhead guard for the operator of the truck to provide improved protection for the operator and better support for the mast while reducing the stresses imposed by the mast on the truck frame.

Other objects as well as the features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a side elevational view of an extensible load lifting mechanism and lift truck constructed in accordance with the present invention with the carriage and mast thereof shown in full lift position.

FIG. 2 is a fragmentary side elevational view of the mast structure of FIG. 1 with the mast in its fully collapsed condition.

FIG. 3 is a top plan view of the mast of FIG. 1.

FIG. 4 is a fragmentary front elevational view of the lower portion of the mast in collapsed condition illustrating the load lifting carriage of the invention.

FIG. 5 is a fragmentary side elevational view of the carriage and mast structure shown in FIG. 19 but on a larger scale.

FIG. 6 is a horizontal section taken on the line 6-6 of FIG. 5.

FIG. 7 is a fragmentary side elevational view of the structure shown in FIG. 5 illustrating by solid lines and in phantom line positions the range of tilting movement of the carriage.

INTRODUCTION The principles of the present invention are applicable to load lifting mechanisms incorporating an extensible framework, commonly termed a mast, made up of one or more sections", depending upon the load lifting capacity and vertical load lifting range desired. The term mast section" refers usually to a rectangular framework made up generally of a pair of horizontally spaced and vertically extending rails suitably interconnected by horizontal braces and adapted to telescopically interengage with the rails of another such section of the mast. The term rails" refers to the vertical side members of a mast section, which may be millformed beam sections, and which are commonly used in pairs in lift mast constructions as the uprights of a mast section. The term ram" as used herein refers to the hydraulically operated piston and cylinder unit employed to impart vertical movement to the load lifting mechanism, and preferably comprises a simple twopart ram made up of a cylinder which constitutes the external member of the ram and an internal plunger which telescopes within the cylinder. However, other known multi-part ram constructions may be employed if desired, as will become apparent hereinafter. The term carriage refers to the apron which travels vertically on the uppermost section of the mast and the forks or other associated cantilevered attachment which directly carries the cargo or load to be raised, lowered and/or transported. The term chain refers to the usual flexible load supporting elements which transmit tension loading and operatively interconnect the ram, mast sections and carriage. These elements preferably comprise the well known link and roller type chains since they operate with a miniumum of friction and stretch, but other types of chains, cables, belts or equivalent elements may be employed if their stretch factor" is suitably taken into account.

FOUR-RAIL CAPACITY" MAST 30 One embodiment of a load lifting mechanism constructed in accordance with the present invention is illustrated in FIGS. 1-7 inclusive and comprises a twosection mast 30 having the lifting range of a conventional four-rail mast. Referring to FIG. 1, mast 30 is shown extended to its full height and mounted in fixed vertical position on a lift truck 32 which may be of the off-the-road type shown or a hard tire industrial type. Despite its high lift range and low collapsed clearance, mast 30 has only two sections, a lower, dual rail section 34 supported near its lower end on the front pin 36 of truck 32, and rigidly connected at its upper end to the rear of truck 32 by an overhead framework 38 which also serves as a safety guard for the operator of the truck. The other, upper section 40 of mast 30 is vertically moveable and slideably telescopes along the outer sides of section 34 when the two sections overlap in the lower lifting range of the mast. Mast 30 is equipped with a load lifting carriage 42 which tracks on section 40, with a two-part ram 44, and with two sets of lift chains 58, 58 and 62, 62'.

Further details of the structure and operation of mast 30 will become apparent from the detailed description of the mast structure as shown in FIGS. 2-7 inclusive which in some instances show only the right-hand comtheir reference numerals have been given a prime mark urn suffix to indicate this relationship.

Carriage 42 has a pair of vertically spaced rollers 46 and 48 linked to an apron 50 of the carriage by a tilting mechanism described hereinafter. Rollers 46, 48 track in the outwardly facing channel or groove 52 defined by the channel-shaped rail 54 of section 40 to thereby guide vertical travel of carriage 42 on section 40 and to provide cantilever support for the apron throughout such travel. A single hydraulic ram 44 is interposed structurally and functionally between sections 34 and 40 to vertically extend mast 30 and to elevate carriage 42 on section 40. Preferably, the lower member of ram 44 is an external cylinder 56 suspended for vertical movement by a first pair of laterally spaced chains 58, 58' from section 34, and the upper member constitutes the ram plunger which is a cylinder-type piston 60 telescopically received in the upper end of cylinder 56. The upper mast section 40 is suspended on plunger 60 by a second pair of laterally spaced chains 62, 62'.

A first pair of counterbalancing arms 64, 64' are rigidly fixed to the upper end of section 40 and extend rearwardly therefrom in outwardly diverging relation to one another on the opposite side of the mast from the forwardly extending forks 66 of carriage 42. A second pair of arms 68, 68' are rigidly fixed to the upper end of section 34 and are oriented in the same manner as arms 64, 64'. A sheave 70 is rotatably supported by arm 64 at the outer end thereof and another sheave 72 is rotatably supported near the fixed end of arm 64 to guide chain 58 along the vertical path of travel of apron 50. Lower arm 68 also rotatably carries two chain sheaves 74 and 76, sheave 74 being vertically aligned with sheave 70 near the outer end of arm 68 and sheave 76 being mounted near the junction of arm 68 and section 34. A pair of sheaves 78, 78' are journalled on the lower end of ram 44, one on each side of cylinder 56, and another pair of sheaves 80, 80' are journalled on the upper end of plunger 60. Chains 58, 58' are each fixed at one end respectively by connections 86, 86' to the upper end of section 34 and have runs 1 l6, 1 16' extending downwardly therefrom to sheaves 78, 78' re spectively, thence are trained around sheaves 78, 78', and have runs 114, 114' extending vertically up to sheaves 76, 76' respectively. Chains 58, 58' then run out to and under sheaves 74, 74', then upwardly in a vertical run 112, 112' to and over sheaves 70,70, then horizontally to and over the respective sheaves 72, 72', and finally downwardly in vertical runs 113, 113' to connection 88, 88' with the uprights of apron 50.

The second pair of chains 62, 62' are fixed at one end 82, 82' to the lower end of section 40 and then extend upwardly in vertical runs 63, 63' over sheaves 80, 80' respectively and then downwardly in vertical runs 65, 65' to connections 84, 84' with the upper end of cylinder 56.

Cylinder 56 is guided for vertical movement relative to section 34 by three horizontally spaced rollers 92 (FIG. 3) preferably journalled on the upper end of section 34 at 120 degree angular intervals for rolling engagement with the outer surface of cylinder 56. A pair of guide rollers 96, 96' are rotatably mounted on the lower end of ram 44 below sheaves 78, 78', one on each side of cylinder 56, and respectively track in the inwardly facing channel grooves of rails 35, 35' of section 34 to guide cylinder 56 for vertical movement between these rails.

Section 40 is slideably guided for vertical movement during the first portion of its upward travel by being telescopically received on lower mast section 34, i.e., the flat inner sides of rails 54, 54' can slide against the fiat outer sides of rails 35, 35' respectively, and a guide plate 100 (FIGS. 1 and 4) extending across the front of section 40 slides along the forward edges of rails 35, 35' during the portion of the travel of section 40 in which it overlaps section 34. However, after being lifted clear of section 34, section 40 is vertically guided solely by a guide bracket 102 rigidly connected to the upper end of plunger 60. Bracket I02 slideably embraces rails 54, 54' of section 40 throughout its range of vertical travel between the fully extended full lift" position of the mast shown in FIG. I and the fully collapsed or completely retracted position of the mast shown in FIG. 2. As a supplement or alternative to bracket 102, a guide tube (not shown) may be telescopically and non-rotatably mounted within plunger 60 and fixed at its upper end to section 40.

It is to be noted that bracket I02 prevents section 40 from twisting or rotating relative to plunger 60, and that carriage rollers 46, 48, and 46', 48 tracking in spaced rails 54, 54 prevent twisting of carriage 42 relative to section 40. Plunger 60 is also slideably keyed against rotation relative to cylinder 56 by axially extending, slideably interengaged key and keyway structure (not shown). This ram-mast section guiding and keying arrangement prevents rotation of section 40 relative to section 34 about the vertical axis of mast 30, an essential feature particularly when sections 40 and 34 are separated from one another during the upper portion of the lifting sequence of mast 30. The plungercylinder keying structure also serves as the principal slide bearing between plunger 60 and cylinder 56, thereby obviating the need for machining the bore of cylinder 56 and thus considerably reducing the cost of manufacturing ram 44.

OPERATION OF MAST 30 The load lifting sequence of operation of mast 30 through its full range begins with the mast in the fully retracted position shown in FIG. 2. Hydraulic fluid is admitted to the lower end of cylinder 56 via hose line from a suitable pressure source, such as the usual hydraulic pump on truck 32, under the control of the truck operator to thereby drive plunger 60 upwardly in cylinder 56 and thus vertically extend ram 44. Cylinder 56 can not move downwardly since it is suspended in the bight of chains 58, 58' which are carrying the weight of the mast section 40 and the load at a 2:1 mechanical advantage compared to the pull of carriage 42 on runs 113, 113'. Hence, so long as carriage 42 can move upwardly relative to section 40, cylinder 56 will remain bottomed in section 34. As plunger 60 is thus moved upwardly from its completely retracted position to partially extended position, which may represent for example a distance of 1% inches of plunger movement, sheaves 80, 80' move upwardly with the plunger and through chains 62, 62' thereby lift section 40 at a 2:1 ratio relative to plunger movement, which for the example given would raise section 40 a distance of three inches. This upward movement of section 40 relative to section 34 separates arms 64, 64' from arms 68, 68' so that chains 58, 58' lift carriage 42 at a 2: l ratio relative to section 40 at the same time chains 62, 62' are lifting section 40. Hence, carriage 42 is lifted at a 4:] ratio relative to the rate of expansion of ram 44, and thus in the example given carriage 42 is lifted 6 inches above its ground level starting position.

Preferably, mast 30 is designed so that arms 64, 64' in the completely retracted condition of the mast are disposed below the uppermost structure of guard 38 of truck 32 by a distance of say three inches (as best seen in FIG. 2). Hence, by the time arms 64, 64' are raised flush with the clearance limit of the truck, carriage 42 will have been lifted twice this distance, thereby providing an initial range of full free lift" of carriage 42 (6 inches) in the aforementioned example) before the uppermost structure of mast section 40 is lifted above the clearance height of the truck and thereafter determines the effective overhead operating clearance required for truck 32.

As plunger 60 moves further upwardly in cylinder 56, this further extension of ram 44 continues to lift section 40 at the 2:1 ratio relative to plunger 60 while the separation of sections 40 and 34 continues to simultaneously lengthen runs 112, 112' of chains 58, 58' between sheaves 70 and 74, thereby lifting carriage 42 further upwardly on section 40 at the 4:l ratio relative to ram extension. When arms 64, 64' reach approximately 47% percent of their travel toward the full lift position (which may represent about 86 ratio of upward movement of forks 66 from their initial starting position), carriage 42 hits stops on section 40. When this occurs, what may be referred to in the art as the normal two-rail action of mast 30 terminates. In other words, at this point in the vertical extension of mast 30, the load being carried on forks 66 catches up with the upper end of mast 30. From this point on upward a true free lift" action will be obtained, i.e., the load on the carriage will move upwardly at the same rate as the upper end of the mast.

As ram 44 continues to expand to its fully extended position, the upward movement of sheaves 80, 80' relative to cylinder 56 causes chains 62, 62' to continue lifting section 40 at a 2:l rate relative to cylinder 56. Since carriage 42 can no longer move up any further on section 40, the further separation of arms 64 and 68 and consequent lengthening of runs 112, 112' shortens the runs 114, 114' and 116, 116 on which cylinder 56 is suspended. Hence, after carriage 42 reaches the top of section 40, the entire ram 44 is lifted upwardly on the lower mast section 34 by chains 58, 58 due to the separation of arms 64 and 68. Thus, the load continues to be lifted on carriage 42 at a 4:l ratio relative to ram expansion.

It is to be noted that during this final stage of vertical mast extension, section 40 is lifted clear of section 34 and becomes widely separated thereform, as best seen in FIG. 1. Hence, in the upper load lifting range of mast 30, the sole connection of carriage 42 to truck 32 is through ram 44 and chains 58, 58' and 62, 62', rather than additionally through a series of telescopically interengaged mast sections as is conventional in the prior art. The final stage of lifting terminates when piston 60 hits a stop at the upper end of cylinder 56. During all of the preceding mast extension stages, section 40 slides vertically upwardly in bracket 102 and piston 60 slides upwardly along its keyed connection with cylinder 56.

The load lowering sequence of mast 30 is the reverse of the aforementioned lifting sequence and is effected by controlled release of hydraulic fluid from cylinder 56 via line 110.

Throughout the load lifting range of mast 30, the load suspended on the cantilever forks 66 of carriage 42 exerts a counterclockwise bending moment (as viewed in FIGS. 1 and 2) on apron 50 which is transmitted to section 40 by the vertically spaced carriage rollers 46, 46' and 48, 48'. This load induced bending moment is, in accordance with a principal feature of the present invention, counterbalanced by a substantially equal bending moment developed by the vertical downwardly directed reaction force transmitted in tension in runs 1 12, 1 12' and acting on arms 64, 64' at the point where chains 58, 58' are trained respectively around sheaves 70, Sheaves 70, 70' are supported on arms 64, 64' at points spaced rearwardly from an imaginary neutral plane defined by runs 113, 113 by a horizontal distance substantially equal to the horizontal spacing between this plane and the center of gravity of the average load on forks 66. Since the counterbalancing force is oriented parallel to and in the same direction as the gravitational force exerted on the load which acts vertically on forks 66 at the load center of gravity, and since these two forces are substantially equal regardless of the weight of the load and act through equal but opposite moment arms, the counterbalancing moment is always substantially equal to the load induced unbalancing moment. This counterbalancing moment is applied to the upper end of section 40 by the rigid cantilever connection of arms 64, 64' to rails 54, 54' respectively. Ram 44 is thus relieved of the cantilevered load bending moment which otherwise would exert a bending stress between plunger 60 and cylinder 56, and between section 40 and bracket 102. Hence, ram 44 sees" only a vertical compression loading from the resultant of the forces applied to it by chains 58, 58' and 62, 62' By eliminating the need for a continuously interconnected telescopic assembly of rail sections hitherto required to take the bending moment exerted by the cantilevered load, the supporting structure of mast 30 need constitute only ram 44 loaded in compression and chains 58, 58' 62, 62' loaded in tension, which is their natural and most efficient mode of loading. Several additional benefits in terms of structural and operational efficiency are obtained throughout the mast and associated truck structure as set forth in the following detailed description of mast 30 and carriage 42.

LOWER MAST SECTION 34 Referring to the structural views of FIGS. 6-13 inclusive, which illustrate an exemplary but presently preferred construction of mast 30, the pair of vertically extending rails 35, 35 of the fixed mast section 34 (FIG. 10) are channel members disposed with their respective grooves 98, 98' facing inwardly toward one another to form tracks for receiving the ram guide rollers 96 and 96 respectively. Rails 35, 35' are rigidly interconnected at their lower ends by a mast mounting bracket (FIG. 2) consisting of a pair of horizontal cross braces 122 and 124 welded to the rear edges of rails 35, 35' and a pair of spaced vertical hanger plates 126 welded between braces I22, I24 and notched to rest on the front mast mounting pin 36 of truck 32.

spectively journalled in spaced upright plates mounted on this bracket structure. bracket. The rear cross brace for the upper end of section 34 is part of the framework of lower arms 68, 68' and includes a cross brace 142 (FIG. 2) connected at one end to a pair of horizontally spaced vertical plates 146', 148' of arm 68' and at the other end to similar plates 146, 148 of arm 68. Sheaves 76', 76 are respectively journalled between plate 146, 148' and 146, 148. The rear ram guide roller 92 is iour nalled between a pair of upright plates 162, 162' fixed on plate 142. Arm 68' has rearwardly converging stringers 150, 152' secured at their forward ends to plates 142', 146' and 148' and at their outer or rear ends to a pair of spaced plates 154' between which sheave 74' is journalled. Plates 142, 146', and 148' and stringer 152' are welded at their inner ends to rail 35' of mast section 34. Arm 68 is constructed in like manner.

Each arm 68, 68' also forms a part of the overhead guide framework 38. Thus, the overhead tubular stringers 156', 156 and 158', 158 of guard 38 are connected at their forward ends respectively to vertical spacers 160' and 160 which are bolted to stringers 152' and 152. Stringers 158' and 158 also extend forwardly to a bolted connection with plate 144 which in turn is bolted to plate 142. The The downwardly inclined rear stringers 162, 162' (FIG. 1) of framework 38 are secured directly to the counterweight structure at the rear end of truck 32. Guard 38 through its above separable bolted connection to mast section 34 maintains the mast in fixed upright position perpendicular to the wheel base of truck 32. Due to the pivotal suspension of section 34 on pin 36, mast 30 exerts only a vertical loading on the forward end of truck 32 and this is applied closely adjacent the front wheels of truck 32. Any tilting loads imposed by the mast are transmitted from the mast solely through guard 38 to the rear of the truck, and hence the truck frame is isolated from such loading.

UPPER MAST SECTION 40 Rails 54, 54' (P16. 3) of moveable mast section 40, like rails 35, 35', are of channel section but are arranged with their grooves 52, 52' facing outwardly to receive the two pairs of vertically spaced carriage rollers 46, 48 and 46', 48 respectively (FIGS. and 7). Rails 54, 54 are spaced horizontally apart so as to receive rails 35, 35' therebetween (FIG. 4) so that section 34 can nest within section 40 in the collapsed, telescoped condition of the mast described previously. Rails 54, 54' are rigidly interconnected at their lower ends by a front cross brace 100, and at their upper ends by the cross bracing interconnecting arms 64, 64'. Each of the arms 64 and 64' is of like construction, arm 64' comprising an upper stringer 170' (FIG. 2) turned down at its outer end and having a pair of spaced vertical plates 172' welded thereto between which sheave 70' is journalled. Arm 64' also has a lower stringer 174' joined at its outer end to plates 172' and at its inner end to another pair of spaced vertical plates 176' (FIG. 2) and 178' (FIG. 3) between which sheave 72' is journalled. Stringer 170' as well as plates 176' and 178' are welded to the associated rail 54' to provide a rigid cantilever connection of arm 64' to section 40. The arms 64 and 64 are cross braced in their rearwardly diverging relation (FIG. 2) by a horizontal plate 180 which extends between and is welded to stringers and 170' and by a V-shaped strut 182 welded at its ends to plates 178 and 178' and along its upper edge to the undersurface of the plate 180. A pair of inclined plates 184 and 184' are welded to the upper ends of rails 54 and 54 respectively over grooves 52 and 52 respectively so as to serve as stops for rollers 46, 46' and thereby define the upper limit of travel of carriage 42 on section 40.

GUlDF BRACKET 102 As best seen in FIGS. 2 and 3, bracket 102 includes a horizontal crosshead 240 secured by bolts 242 to the cap of plunger 60, and a rectangular front frame consisting of two vertical plates 244 and 244' and top and bottom horizontal braces 246 welded to the from face of crossheud 240 so that plates 244 and 244' extend parallel to and spaced outwardly from the front faces of rails 54 and 54' respectively. Bracket 102 also includes vertically extending side plates 250 and 250 secured along their forward edges to plates 244 and 244' respectively and disposed in closely spaced relation between rails 54 and 35 and 54' and 35' respectively. Bracket 102 has a series of wear pads for sliding engagement with each rail 54, 54', these pads being arranged in two vertically spaced pairs forward pairs 252, 252' and two vertically spaced rearward pairs 256, 256' to slideably bear against the front and rear surfaces of rail 54'. Pads 252, 252 are fixed to plate 244' and pads 256, 256' to a flanges 250, 251' (FIG. 3) of plates 250, 250'. Bracket 102 is thus capable of guiding vertical travel of mast section 40 relative to ram 44 and thus provides a safety factor for off-center loads and chain malfunctions in that it can withstand any unbalanced bending stresses imposed by carriage 42 on section 40 within the capabilities of ram 44 to accept such bending stresses.

CHAIN REEVING STRUCTURE Sheaves 78 and 78' are supported by a suitable bracket structure (not shown) fixed to the outer surface of cylinder 56 near the lower end thereof. This bracket structure carries the spindles for sheaves 78 and 78' arranged so that the sheaves are mounted at an angle corresponding to the associated arms 68, 68'. This bracket structure also has suitable spindles below sheaves 78 and 78' for mounting the, ram guide rollers 96 and 96' adjacent the lower end of cylinder 56 with these rollers disposed to track in grooves of rails 35 and 35' respectively.

The connection 88 and 88' of chains 58 and 58' with the carriage 42 is best seen in FIGS. 2 and 5 and consists of bolts 89 and 89' adjustably secured to arms 264 and 264' respectively which extend rearwardly from the main links 266 and 266' of the carriage tilting mechanism described hereinafter. The connections 86, 86' of the other ends of chains 58, 58' to mast section 34 consists of bolts 266, 266' respectively secured to chain runs 116 and 116' (FIG. 2) and anchored with respect to rails 35, 35'. The connections 84 and 84' of chains 62 and 62' to cylinder 56 consist of suitable brackets welded to the outer surface of cylinder 56 near the upper end thereof to which are secured suitable chain connecting bolts. The connections 82 and 82' at the other ends of chains 62 and 62' with the upper mast section 40 (FIG. 1 1 and 12) consist of suitable brackets welded to plate 100 at its junctions with rails 54 and 54' and suitable chain connector bolts respectively secured to these brackets. Sheaves 80 and 80' are joumalled on axles between spaced plates 280, 282 and 280', 282' (FIGS. 3) mounted on the opposite sides of crosshead 240 and angularly oriented so that sheaves 62 and 62 are properly aligned with the associated fore and aft runs of chains 62 and 62.

TILTING CARRIAGE 42 Carriage 42 of mast 30 comprises a novel tilting carriage constructed in accordance with the present invention as shown by way of example in FIGS. 2-5 inclusive. Refering to FIGS. 2 and 5, carriage 42 has a pair of main links or tie bars 266 and 266' suspended respectively from chains 58 and 58' as described previously. Tie bar 266 extends vertically adjacent the outer side of rail 54, and bar 266' is suspended in like manner adjacent the outer side of rail 54'. Carriage rollers 46 and 48 are respectively journalled on axle pins 290 and 292 which extend through and are secured to the upper and lower ends respectively of tie bar 266. Upper and lower pivot links 294 and 296 are pivoted at their rear ends on pins 290 and 292, axially intermediate the tie bar and roller, and extend forwardly of the mast in converging relation to one another. The forward ends of links 294 and 296 extend between, and are pivotally connected by vertically spaced pins 298 and 300 respectively to, a pair of vertical plates 302 and 304 which form part of apron 50 of carriage 42 (see also FIG. 4). Plates 302 and 304 are separated by spacers 306 and 308 (FIGS. 4 and 5) and are welded in notches of upper and lower apron rails 310 and 312, the front faces of apron rails 310 and 312 being flush with the front faces of plates 302 and 304. The left-hand side of carriage 42 has like parts 290 '308' inclusive (FIG. 2).

The upper edge of rail 310 is provided with a series of notches 314 adapted to removably receive the upper hook ends 316 (FIG. 5) of the L-shaped forks 66. The upright backs 318 of forks 66 bear against rails 310, 312 to provide the cantilever support for the forwardly projecting tines 320 of forks 66. Various other load lifting attachments may be removably secured to carriage 42 in like cantilever fashion.

Carriage 42 is equipped with two hydraulic rams 322 and 322' respectively mounted on tie bars 266 and 266' inwardly of the associated tie bar so as to swing in the space available between the respective tie bars and grooves 52, 52 of the associated rails 54, 54' (FIGS. 5 and 7). Ram 322 includes a cylinder 324 pivoted at its upper end on a pin 326 secured to bar 266 just beneath link 294 and a plunger 328 hydraulically reciprocated in cylinder 324 and extending from the lower end thereof. The lower end of plunger 328 is pivotally connected by a pin 330 to a block 332 fixed to an apron crank arm 334 which in turn is secured at its forward end to plate 304 and spacer 308. Ram 322' is mounted in like manner between bar 266' and apron 50.

Rams 322, 322 are conventional and of the double acting type supplied with pressure fluid from a common source via hose lines 336, 336 and 338, 338' which are connected to supply-exhaust lines 340 and 342 (FIG. 4). Lines 340 and 342 are clamped by a bracket 346 (FIG. 2) to the outer side of bar 266' and then run upwardly over a sheave 348 journalled on a pin 350 of a housing 352 which in turn is spring mounted on plate 176. Lines 340, 342 then run downwardly to a dual sheave 360 suitably secured to cylinder 56 near the lower end thereof. Lines 340, 342 then run upwardly to a connector 364 (FIG. 2), and then run back downwardly to truck 32 to a connection with the source of hydraulic pressure fluid, a suitable hydraulic control mechanism being provided convenient to the truck operator to control tilt of carriage 42 independently of load lifting on mast 30.

Rams 322 and 322' are controlled to operate identically and simultaneously to extend and retract their plungers 328, 328' to thereby articulate the associated carriage framework which in turn acts in the manner of a four-bar linkage whereby fork tines 320, 320' are moved through a range of tilting movement as illustrated in FIG. 7 by the solid and broken line views thereof. Only the operation of the right-hand linkage will be explained since the same explanation applies to the left-hand linkage. Tie bar 266 acts as the fixed link of the four-bar linkage since it is anchored by carriage rollers 46 and 48 tracking in rail groove 52. In order to lower forks 66 toward their extreme downwardly tilted position shown in broken lines in FIG. 7, ram 322 is operated to draw plunger 328 upwardly into cylinder 324, thereby exerting through crank 334 a clockwise moment on apron 50 which pivots links 296 and 298 upwardly or counterclockwise as viewed in FIGS. 5 and 7. To tilt forks 66 in the opposite direction toward their extreme upwardly inclined position shown in solid lines in FIG. 7, ram 322 is operated in the opposite direction to force plunger 328 downwardly so that a counterclockwise moment is exerted through crank 334 on apron 50.

The above described tilting carriage mechanism provides an economical and efficient means for varying the attitude of fork tines 320, 320' or other load lifting attachment carried on apron 50 without requiring that mast 30 be tilted from its fixed orientation relative to truck 32, thereby retaining the operating capabilities of a truck equipped with a conventional tilting mast while eliminating several disadvantages of such masts. Due to the generally vertical orientation and limited swing required of rams 322, 322', they may be compactly nested inwardly of tie bars 266, 266' in rail grooves 52, 52' of rail 54, 54', thereby reducing the overall width of the mast. Since the mast normally nests between the front tires of the lift truck, this reduction in mast width permits a concomitant reduction in the overall width of the truck to better facilitate operation in narrow aisles and cramped storage spaces.

It is also to be noted that apron 50 forms the shorter of the two long" links of the four-bar linkage. This orients the center of pivotal motion of the load outside the linkage at the intersection P of the imaginary lines 370 and 372 (FIG. 7) projected perpendicularly from two positions of the same point on the apron in its range of tilting movement. Hence, the load pivot point is extended out to point P which is preferably near or coincident with the center of gravity of the average load to be carried on forks 66. Therefore, the tilting motion imparted to the forks 66 neither raises nor lowers the load but rather pivots the same about its center of gravity. Due to this feature, small size rams 322, 322' are sufiicient to articulate the carriage since they need only overcome the frictional resistance of the carriage parts. The four-bar linkage also permits a relatively short stroke ram 322 to be used for obtaining a relatively large angular range of motion of the carriage. These features in turn lead to other economies of structure as well as to reduced drain on the truck pump and power source.

with the aforementioned linkage suspension, the upper and lower ends of apron 50 move in opposite directions to tilt the forks, which minimizes the space required between the mast and apron for a given range of tilting motion and thus reduces the load moment arm. The four-bar tilting linkage of carriage 42 also permits carriage rollers 46, 48 to be spaced vertically farther than the height of apron S0 to better distribute the bending load exerted by forks 66 along the rails of mast section 40. Although other articulations of rams 322, 322' may be used, such as directly between bar 266 and apron 50, the provision of crank arm 334 to couple ram 322 to apron 50 enables the ram to retain its preferred vertical orientation while acting between the two long links of the four-bar linkage, thereby obtaining a force multiplication for rams 322, 322'.

Carriage 42 also cooperates with mast 30 to improve the performance of lift truck 32 in several respects. By using a tilting carriage, mast 32 need not be mounted for tilting movement on truck 32 and hence the position of the load on carriage 42 need not be shifted away from the center of the truck. This improves the stability of the mast and truck and increases the capacity of the mast over one which must tilt. Also, since mast 30 need not swing in order to tilt the load, the inertia forces tending to produce whip action of the mast are greatly reduced. The combination of the tilting carriage 42 and non-tilting mast 30 also permits lower chain orienting arms 68 to be fixedly attached or anchored near their outer ends to the lift truck, which in turn enables them to be incorporated with the overhead guard framework 38, thereby relieving mast section 34 of the bending stress imparted to arms 68, 68' and providing greatly increased side support for the mast so that the mast and truck can operate at a much greater angle of side tilt.

I claim:

1. A mast section and carriage sub-assembly for an extensible lift truck mast including in combination a mast section comprising first and second upright rails each having a longitudinal channel, first and second tie bars disposed respectively adjacent said channels of said first and second rails and extending parallel thereto, each of said tie bars having first and second rollers rotatably carried thereon and disposed in tracking relation in the associated channel, each of said tie bars having first and second links pivotally connected to said tie bar at vertically spaced points, said links extending forwardly of said mast section adjacent the sides of said rails in converging relationship relative to one another, apron means disposed laterally across and spaced forwardly of said rails, said apron means being carried by said links with said first and second links being pivotally connected to said apron means respectively at co-axially aligned first points and co-axially aligned second points spaced vertically from said first points, first and second hydraulic rams respectively pivotally connected at one end thereof to said first and second tie bars adjacent said first links, said apron means including first and second crank arms fixed thereto and extending toward said first and second tie bars and being pivotally connected to the opposite ends of said first and second rams respectively, and means for supplying pressure fluid to said rams to operate the same simultaneously and in synchronism with one another, each of said tie bars having a first axle mounted on said tie bar adjacent the upper end thereof. said first link and said first roller associated with each of said tie bars being journalled on said first axle, each of said tie bars having a second axle mounted on said tie bar adjacent the lower end thereof, said second link and second roller associated with each tie bar being journalled on said second axle, said rails being disposed with said channels thereof facing outwardly opposite to one another and said rams being disposed between the associated tie bar and rail in nesting relation in said channel of the associated rail for limited swinging movement within the confines of said channel.

2. A tilting carriage mechanism comprising upright tie bar means adapted to engage a support for vertical movement thereon and to restrain said tie bar means against tilting relative to said support, apron means disposed generally upright in horizontally spaced relation from said tie bar means and having load supporting means thereon extending generally horizontally away from said tie bar means, first and second link means individually pivotally connected to said tie bar means and to said apron means at points spaced vertically from one another, the vertical spacing between said tie bar connection points of said link means being greater than that between said apron connection points of said link means, and means for tilting said apron means relative to said tie bar means, said tie bar means, said apron means and said link means together forming a four-bar linkage wherein said tie bar means and said apron means serve as the longest links of said linkage with said apron means being the shorter of such longest links, the vertical spacing of said connection points and the dimensions of said four-bar linkage being correlated with a load carrying space defined by said apron means and said load support means such that, in response to said tilting of said apron means, an average size load carried on said load support means and occupying the load carrying space pivots about a point spaced above said load support means and spaced horizontally outwardly from the side of said apron means remote from said tie bar means with said load pivot point being generally in the vicinity of the center of gravity of the average size load to thereby minimize vertical lifting movement of the average size load dur ing tilting thereof on said carriage mechanism.

3. The combination set forth in claim 2 wherein said tilting means comprises a hydraulic ram pivotally connected to said tie bar means and to said apron means.

4. The combination set forth in claim 2 wherein said tilting means comprises a hydraulic ram pivotally connected to said tie bar means adjacent said connection of said first link means with said tie bar means, said apron means including a crank arm fixed thereto extending toward said tie bar means, said ram being pivotally connected to said crank arm.

5. The combination as set forth in claim 2, wherein said support comprises first and second upright rails, first and second roller means disposed for tracking movement vertically along said rails and operably connected to said tie bar means, said first link means and said first roller means being journalled on a first axle means which is mounted on said tie bar means adjacent the upper end of said tie bar means, said second link means and said second roller means being journalled on a second axle means which is mounted on said tie har means adjacent the lower end of said tie bar means. i a

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 3,913,765

DATED 1 October 21, 1975 INVENTOR(S) Keith E. Ramsey It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown betow:

Column 1, line 3Q "carrier" should be -carried-- Column 1, line 62 "19" should be -4- "ratio" should be -inches Column 5, line 31 Column 7, line 6 delete "bracket" (second occurrence) Signed and Sealed this RUTH C. MASON C. MARSHALL DANN Arresting ()jfl'cer ('ummissr'mu-r uflarmls and Trudvmurks 

1. A mast section and carriage sub-assembly for an extensible lift truck mast including in combination a mast section comprising first and second upright rails each having a longitudinal channel, first and second tie bars disposed respectively adjacent said channels of said first and second rails and extending parallel thereto, each of said tie bars having first and second rollers rotatably carried thereon and disposed in tracking relation in the associated channel, each of said tie bars Having first and second links pivotally connected to said tie bar at vertically spaced points, said links extending forwardly of said mast section adjacent the sides of said rails in converging relationship relative to one another, apron means disposed laterally across and spaced forwardly of said rails, said apron means being carried by said links with said first and second links being pivotally connected to said apron means respectively at co-axially aligned first points and co-axially aligned second points spaced vertically from said first points, first and second hydraulic rams respectively pivotally connected at one end thereof to said first and second tie bars adjacent said first links, said apron means including first and second crank arms fixed thereto and extending toward said first and second tie bars and being pivotally connected to the opposite ends of said first and second rams respectively, and means for supplying pressure fluid to said rams to operate the same simultaneously and in synchronism with one another, each of said tie bars having a first axle mounted on said tie bar adjacent the upper end thereof, said first link and said first roller associated with each of said tie bars being journalled on said first axle, each of said tie bars having a second axle mounted on said tie bar adjacent the lower end thereof, said second link and second roller associated with each tie bar being journalled on said second axle, said rails being disposed with said channels thereof facing outwardly opposite to one another and said rams being disposed between the associated tie bar and rail in nesting relation in said channel of the associated rail for limited swinging movement within the confines of said channel.
 2. A tilting carriage mechanism comprising upright tie bar means adapted to engage a support for vertical movement thereon and to restrain said tie bar means against tilting relative to said support, apron means disposed generally upright in horizontally spaced relation from said tie bar means and having load supporting means thereon extending generally horizontally away from said tie bar means, first and second link means individually pivotally connected to said tie bar means and to said apron means at points spaced vertically from one another, the vertical spacing between said tie bar connection points of said link means being greater than that between said apron connection points of said link means, and means for tilting said apron means relative to said tie bar means, said tie bar means, said apron means and said link means together forming a four-bar linkage wherein said tie bar means and said apron means serve as the longest links of said linkage with said apron means being the shorter of such longest links, the vertical spacing of said connection points and the dimensions of said four-bar linkage being correlated with a load carrying space defined by said apron means and said load support means such that, in response to said tilting of said apron means, an average size load carried on said load support means and occupying the load carrying space pivots about a point spaced above said load support means and spaced horizontally outwardly from the side of said apron means remote from said tie bar means with said load pivot point being generally in the vicinity of the center of gravity of the average size load to thereby minimize vertical lifting movement of the average size load during tilting thereof on said carriage mechanism.
 3. The combination set forth in claim 2 wherein said tilting means comprises a hydraulic ram pivotally connected to said tie bar means and to said apron means.
 4. The combination set forth in claim 2 wherein said tilting means comprises a hydraulic ram pivotally connected to said tie bar means adjacent said connection of said first link means with said tie bar means, said apron means including a crank arm fixed thereto extending toward said tie bar means, said ram being pivotally connected to said crank arm.
 5. The combination as set forth in claim 2, wherein said support comprises first and second upright rails, first and second roller means disposed for tracking movement vertically along said rails and operably connected to said tie bar means, said first link means and said first roller means being journalled on a first axle means which is mounted on said tie bar means adjacent the upper end of said tie bar means, said second link means and said second roller means being journalled on a second axle means which is mounted on said tie bar means adjacent the lower end of said tie bar means. 